Typical rotors for outside rotor electric machines usually include a retaining ring which retains the magnets and is connected to the rotating shaft through a flange. Due to increased rotor speed and thermal deflections, the retaining ring tends to undergo a radial displacement which increases the air gap between the rotor and stator. Because the retaining ring is generally stiffer in proximity of the flange, the radial displacement is generally greater axially away from the flange than in proximity thereof. As such, during use the retaining ring usually tends to adopt a somewhat conical shape. Such deformation generally makes it difficult to appropriately size the air gap, and can lead to magnet cracks due to unequal support of the magnets. In addition, as the retaining ring deflects in a conical manner, the magnets can become inclined enough such as to produce an axial force which pushes the magnets out of their position on the retaining ring.
Accordingly, improvements are desirable.